F. K. Kong MA, MSc, PhD, CEng, FICE, FIStructE, R. H. Evans CBE, DSc, D ès Sc, DTech, PhD, CEng, FICE, FIMechE, FIStructE (auth.)-Reinforced and Prestressed Concrete-Springer US (1987)

Johansen's stepped yield criterion 299
A~ m' calculated from A; only
7
As m calculated from As only
Fig. 8.3-6 Slab with top and bottom reinforcement
of reinforcement. Similarly, where a slab is reinforced with both top and
bottom reinforcement, as in Fig. 8.3-6, the positive yield moment m is
calculated from the bottom steel As by ignoring the existence of the top
steel A;; the negative yield moment m' is calculated from the top steel A~
by ignoring the existence of the bottom steel As. (See Example 8.4-4.)
Example 8.3-1
A skew slab is rigidly supported along two opposite edges and unsupported
along the other two edges (Fig. 8.3-7(a) ). The top and bottom reinforcement
each consists of two unequal bands of bars respectively parallel to the
supported and unsupported edges. Determine the normal moments on
all the yield lines for the assumed patterns in Fig. 8.3-7(b) and (c).
SOLUTION
For yield-line pattern in Fig. 8.3-7 (b)
(mn)ab = (mn)te = m2 cos2 a (from Fig. 8.3-8(a) and eqn 8.3-7)
For yield-line pattern in Fig. 8.3-7 (c)
(mn)ef = mz cos 2 a (as for (mn)ab above)
(mn)eh = m 1 cos 2 a (from Fig. 8.3-8(b) and eqn 8.3-7)
(mn)ej = m1 cos2 (~- {3) + m2 cos2 ({3 - a)
:mt
I
I
I
I
~2
Moment
axes
Fig. 8.3-7(a)